In a DC power feeding operation, an arc discharge is generated disadvantageously when an electric switch or outlet is disconnected.
In general, in both DC and AC operations, an arc discharge is generated when power is disconnected. In the case of the AC operation, there is an instant where a voltage changes to zero in every 10 ms if a frequency is set to 50 Hz (refer to FIG. 10). Therefore, the arc discharge stops within 10 ms spontaneously.
In comparison, in the case of the DC operation, there is no instant of the zero voltage. Therefore, the arc discharge does not stop spontaneously.
As an arc discharge is generated, heat may be generated, and an electric contact may be damaged, so that wiring in a disconnection point may be melt to cause a fire. In addition, this may generate light or sound, which may make a user fear or shocked, so that a secondary failure may occur.
For this reason, there have been proposed some electric outlets having a spring switch mechanism or a mechanism capable of suppressing an arc discharge by using a magnetic force. However, in these methods, a structure of the electric outlet becomes complicated, and cost increases. Furthermore, it is difficult to answer a failure such as electric disconnection.